An authenticating system comprises an information processing device and an authentication server connected over a network. The information processing device includes: a storage part for storing user registration information with which the identification information of each user and authentication information other than a password are registered; an authentication information acquiring part for acquiring the authentication information based on receiving a user's instruction; an identification information acquiring part for acquiring the identification information corresponding to the authentication information by running a search through the user registration information; an authentication requesting part for generating the authentication request including the identification information and sending the generated authentication request to the authentication server; a receiving part for receiving the result of the authentication from the authentication server; and a controlling part for putting the information processing device into a logged-in state in accordance with the result of the authentication.